UPDATE: St. Croix County is under a tornado warning
At 2:46 p.m. Wednesday, the National Weather Service office at Chanhassen, Minn., issued a tornado warning for southern St. Croix County, northern Pierce County and extreme southwestern Dunn County.
The warning is in effect until 3:30 p.m.
At 2:41 p.m., radar indicated a storm capable of producing a tornado.
The most dangerous part of the storm was six miles southwest of River Falls, or about five miles northeast of Prescott.
The storm was moving east at 35 mph.
Law enforcement reported a rotating wall cloud near Roberts at 2:45 p.m.
Communities in the warning area include River Falls, Ellsworth, Burkhardt, Beldenville, Roberts, Martel, Hammond, Baldwin, Woodville, Spring Valley, Elmwood and Hersey.
When a tornado warning is issued based on radar it means that strong rotation has been detected in the storm. A tornado may already be on the ground, or one is expected to develop shortly.
A tornado watch remains in effect until 4 p.m. for St. Croix and the Twin Cities region.
The Weather Service said conditions point to the potential for a significant severe weather outbreak across parts of the area from this afternoon through early evening.
The threat for severe weather exists across the entire Minneapolis-St. Paul metropolitan area, the Weather Service said, but the greatest threat exists from along the I-35 corridor and east from this afternoon into the early evening.
The potential for very large hail, damaging wind and tornadoes will be present, especially across the enhanced risk area, the Weather Service said on its Web site.
Tornadoes can develop quickly from severe thunderstorms, officials warned.
If a tornado is spotted, people in the area of it should act quickly and move to a safe place inside a sturdy structure, such as a basement or small interior room.
There was a severe thunderstorm warning for the northern Wisconsin counties of Polk, Barron, Burnett, Washburn, Sawyer, Douglas, Ashland and Bayfield Wednesday morning.
At 10:48 a.m., Doppler radar indicated a line of severe thunderstorms capable of producing destructive winds in excess of 80 mph.
The storms were along a line extending from Washburn to Chippewa Lake to Birchwood.
The storms were moving at 55 mph and had the potential to produce nickel-size hail, the Weather Service said.
"These storms have a history of producing widespread wind damage across eastern Minnesota and much of northwest Wisconsin," the Weather Service warned on its website. "Significant damage to trees and powerlines is expected. Falling trees may also cause damage to cars and buildings."
The Hudson Fire Department was dispatched to a report of a power pole on fire near County A and Daily Road in the town of Hudson at about 11:30 a.m. Wednesday.